Graphene-coated high-entropy oxide nanoparticle catalyst and preparation method and application thereof

Abstract

The present application relates to the technical field of electrolysis of water, and provides a graphene-coated high-entropy oxide nanoparticle catalyst as well as a preparation method and application thereof. The present application uses transition metal salt as a high-entropy oxide precursor and uses mesoporous carbon as a reducing carrier. First, metal ions are dispersed into the interior of the mesoporous carbon by mixing. Then, the metal ions are reduced and melted into a shape by utilizing the characteristic of Joule heating in which the temperature is raised to a high temperature in a very short time, and the graphene-coated high-entropy oxide nanoparticle catalyst is prepared by rapid cooling. The preparation method provided by the present application is simple, fast and efficient, and the graphene-coated high-entropy oxide nanoparticle catalyst prepared by the method exhibits excellent electrocatalytic performance in the electrolysis of water, oxygen evolution, hydrogen evolution and overall water splitting reaction.

Description

Technical Field

[0001] This invention relates to the field of water electrolysis technology, and in particular to a graphene-coated high-entropy oxide nanoparticle catalyst, its preparation method, and its application. Background Technology

[0002] Hydrogen production through water electrolysis is a strategic direction for the development of recyclable energy. A key factor hindering its large-scale industrial application lies in the slow kinetics of the hydrogen evolution and oxygen evolution electrode reactions during water electrolysis. Therefore, preparing highly active and stable electrode catalytic materials is crucial for the large-scale application of water electrolysis hydrogen production technology. High-entropy electrocatalysts, due to their high entropy stability, low resistivity, structural stability, and corrosion resistance, exhibit excellent electrocatalytic performance and have attracted extensive research. High-entropy electrocatalysts possess multi-component compositions; the preparation of electrocatalysts using combinations of five or more metals offers more controllable parameters and a wider controllable space.

[0003] High-entropy electrocatalysts are currently a hot research topic, exhibiting advantages such as high stability, high current density, and high activity in electrocatalytic reactions. The preparation methods for high-entropy electrocatalysts are diverse, currently mainly involving mechanical ball milling, laser additive manufacturing, and magnetron sputtering. Mechanical ball milling involves physical deformation, cold welding, and crushing of various metal powders under ball milling conditions, ultimately achieving atomic-level mixing and alloying of metal elements. Laser additive manufacturing uses various metal powders as raw materials, melting and depositing them into shape using high-energy lasers according to a programmed sequence via a computational system. Magnetron sputtering involves placing a substrate and sputtering target at positive and negative electrodes respectively, applying a high voltage between the electrodes to generate plasma, bombarding the target, causing target atoms to detach and deposit onto the substrate surface, thus preparing materials with high-entropy structures. However, these methods have drawbacks: they are complex to operate, and the large differences in melting points among different metals make it difficult to form nanoparticles with high specific surface areas, which is detrimental to the catalytic reaction. Summary of the Invention

[0004] In view of this, the present invention provides a graphene-coated high-entropy oxide nanoparticle catalyst, its preparation method, and its application. The graphene-coated high-entropy oxide nanoparticle catalyst provided by the present invention has a large specific surface area, high dispersion, high catalytic activity, good stability, and its preparation method is simple and rapid.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] A method for preparing a graphene-coated high-entropy oxide nanoparticle catalyst includes the following steps:

[0007] Mesoporous carbon and a mixed metal salt solution are mixed and then dried to obtain a mixture of metal salt and mesoporous carbon; the metal elements in the mixed metal salt solution include at least five of Fe, Co, Ni, Cr, V, Ti, Cu, and Mn, and the molar amounts of each metal element are equal;

[0008] The mixture of the metal salt and mesoporous carbon is spread on the surface of carbon cloth, and the carbon cloth is Joule heated to cause the metal salt and mesoporous carbon to react, thus obtaining a graphene-coated high-entropy oxide nanoparticle catalyst.

[0009] Preferably, the Joule heating method includes: connecting the two ends of the carbon cloth to the positive and negative terminals of a power source, and performing Joule heating by energizing the power source; the intensity of the current used for energizing the power source is 10 to 35 A.

[0010] Preferably, the Joule heating is carried out in an oxygen-containing atmosphere; the temperature of the carbon cloth surface after Joule heating is 1000-2000℃; and the reaction time is ≤2s.

[0011] Preferably, the mixture of metal salt and mesoporous carbon is spread at an amount of 10–500 mg / cm² on the carbon cloth surface. 2 .

[0012] Preferably, the total concentration of metal ions in the mixed metal salt solution is 0.01–0.1 mol / L; the ratio of mesoporous carbon to the mixed metal salt solution is 5–25 mg:1 mL.

[0013] Preferably, the mesoporous carbon is pretreated before use; the pretreatment method includes: mixing the mesoporous carbon and nitric acid for heat treatment, and then washing and drying the heat-treated mesoporous carbon in sequence.

[0014] The present invention also provides a graphene-coated high-entropy oxide nanoparticle catalyst prepared by the preparation method described above, comprising high-entropy oxide nanoparticles and a graphene layer coated on the surface of the high-entropy oxide nanoparticles; the metal element in the high-entropy oxide includes at least five of Fe, Co, Ni, Cr, V, Ti, Cu, and Mn.

[0015] Preferably, the metal element in the high-entropy oxide is Fe, Co, Ni, Cr and V, or Fe, Co, Ni, Cr and Mn.

[0016] The present invention also provides the application of the graphene-coated high-entropy oxide nanoparticle catalyst described above in the catalytic electrolysis of water reaction.

[0017] Preferably, the water electrolysis reaction is an oxygen evolution reaction, a hydrogen evolution reaction, or a complete water electrolysis reaction.

[0018] This invention provides a method for preparing a graphene-coated high-entropy oxide nanoparticle catalyst, comprising the following steps: sequentially mixing and drying mesoporous carbon and a mixed metal salt solution to obtain a mixture of metal salt and mesoporous carbon; the metal elements in the mixed metal salt solution include at least five of Fe, Co, Ni, Cr, V, Ti, Cu, and Mn, and the molar amounts of each metal element are equal; spreading the mixture of metal salt and mesoporous carbon on the surface of carbon cloth, and subjecting the carbon cloth to Joule heating to cause the metal salt and mesoporous carbon to react, thereby obtaining a graphene-coated high-entropy oxide nanoparticle catalyst. This invention uses transition metal salts as high-entropy oxide precursors and mesoporous carbon as a reducing support. First, metal ions are dispersed into the interior of the mesoporous carbon through mixing and drying. Then, utilizing the characteristic of Joule heating to reach high temperatures in an ultra-short time, the metal ions are reduced, melted, and shaped by the instantaneous high temperature generated when an electric current passes through the carbon cloth. Rapid cooling then completes the process, producing homogeneous and stable high-entropy oxide nanoparticles. Simultaneously, a graphene layer forms on the surface of the high-entropy oxide nanoparticles during the high-temperature reduction of metal ions on the mesoporous carbon support. The method provided by this invention is convenient to operate, has a short preparation time, and Joule heating can be completed instantaneously, with a reaction time of no more than 2 seconds, significantly reducing time costs compared to existing technologies.

[0019] The graphene-coated high-entropy oxide nanoparticle catalyst prepared by this invention possesses a single-phase structure and good conductivity, which is beneficial for improving charge transfer efficiency during the catalytic reaction and reducing the overpotential required for the reaction. Furthermore, the high-entropy oxide nanoparticles in the catalyst prepared by this invention have high dispersion and large specific surface area, which is conducive to the occurrence of electrocatalytic reactions. Graphene, acting as a conductive substrate and forming a coating structure on the surface of the high-entropy oxide nanoparticles, can inhibit the corrosion of the high-entropy oxides by the electrolyte, which is beneficial for the electrocatalytic reaction and can improve the stability and extend the service life of the catalyst. The graphene-coated high-entropy oxide nanoparticle catalyst prepared by this invention exhibits excellent electrocatalytic performance in oxygen evolution, hydrogen evolution, and total water splitting reactions. The results of the examples show that the graphene-coated high-entropy oxide nanoparticle catalyst prepared by this invention achieves a current density of 10 mA cm⁻¹ for catalyzing the oxygen evolution and hydrogen evolution reactions. -2 At that time, the overpotential of the catalyst prepared by the present invention was reduced by 137 mV and 228 mV respectively compared with that prepared by the conventional method; the graphene-coated high-entropy oxide nanoparticle catalyst prepared by the present invention achieved a current density of 100 mA cm⁻¹ for the total water splitting reaction. -2 At that time, the voltage for water electrolysis is 1.7 to 1.8V. Attached Figure Description

[0020] Figure 1 G@(FeCoNiCrV)O prepared in Example 1 x Transmission electron microscopy image of the catalyst;

[0021] Figure 2 G@(FeCoNiCrV)O prepared in Example 1 x X-ray diffraction pattern of the catalyst;

[0022] Figure 3 G@(FeCoNiCrV)O prepared in Example 2 x Results of oxygen evolution (a) and hydrogen evolution (b) performance tests of the catalyst. Detailed Implementation

[0023] This invention provides a method for preparing a graphene-coated high-entropy oxide nanoparticle catalyst, comprising the following steps:

[0024] Mesoporous carbon and a mixed metal salt solution are mixed and then dried to obtain a mixture of metal salt and mesoporous carbon; the metal elements in the mixed metal salt solution include at least five of Fe, Co, Ni, Cr, V, Ti, Cu, and Mn, and the molar amounts of each metal element are equal;

[0025] The mixture of the metal salt and mesoporous carbon is spread on the surface of carbon cloth, and the carbon cloth is Joule heated to cause the metal salt and mesoporous carbon to react, thus obtaining a graphene-coated high-entropy oxide nanoparticle catalyst.

[0026] This invention involves mixing mesoporous carbon and a mixed metal salt solution, followed by drying, to obtain a mixture of the metal salt and mesoporous carbon. In this invention, the pore size of the mesoporous carbon is preferably 2–5 nm, and the specific surface area is preferably 1400–1500 m². 2 / g; the mesoporous carbon is preferably pretreated before use; the pretreatment method preferably includes: mixing mesoporous carbon and nitric acid for heat treatment, and washing and drying the heat-treated mesoporous carbon in sequence; the nitric acid is preferably concentrated nitric acid (mass fraction of 65% to 68%); the ratio of mesoporous carbon to nitric acid is preferably 100 to 500 mg: 5 to 15 mL, more preferably 200 to 400 mg: 8 to 12 mL; the heat treatment temperature is preferably 120°C, the time is preferably 12 h, and the heat treatment is preferably carried out in a hydrothermal reactor; after the heat treatment is completed, the resulting liquid is preferably cooled to room temperature and then filtered to obtain the heat-treated mesoporous carbon; the present invention uses nitric acid to heat treat mesoporous carbon, which can remove metal impurities in mesoporous carbon and modify oxygen-containing functional groups on mesoporous carbon, which is beneficial to the loading of metal salts; the washing agent is preferably deionized water, and the number of washings is preferably 3 times; the drying temperature is preferably 160°C, and the time is preferably 12 h; the present invention obtains clean mesoporous carbon through pretreatment.

[0027] In this invention, the metal elements in the mixed metal salt solution include at least five of the following: Fe, Co, Ni, Cr, V, Ti, Cu, and Mn, preferably five, and the molar amounts of each metal element are equal, more preferably including Fe, Co, Ni, Cr, and V; this invention does not have special requirements on the type of metal salt in the mixed metal salt solution, and any soluble salt corresponding to the above-mentioned metal elements can be used, such as nitrates or hydrochlorides; in specific embodiments of this invention, the metal salts used are preferably Fe(NO3)3, Ni(NO3)2, Co(NO3)2, Mn(NO3)2, CuCl2, and NaVO3; the total concentration of metal ions in the mixed metal salt solution is preferably 0.01–0.1 mol / L, more preferably 0.04–0.08 mol / L; the ratio of the amount of mesoporous carbon to the mixed metal salt solution is preferably 5–25 mg:1 mL, more preferably 10–20 mg:1 mL, wherein the mass of the mesoporous carbon is based on the mass of the pretreated mesoporous carbon.

[0028] In this invention, the mesoporous carbon and the mixed metal salt solution are preferably mixed by ultrasonic mixing, with the ultrasonic mixing power preferably being 250-750W and the time preferably being 1h-4h; after ultrasonic mixing is completed, the resulting mixture is dried, with the drying temperature preferably being 60℃ and the drying time preferably being 8h.

[0029] After obtaining a mixture of metal salt and mesoporous carbon, this invention spreads the mixture onto the surface of carbon cloth, and then subjectes the carbon cloth to Joule heating to allow the metal salt and mesoporous carbon to react, thereby obtaining a graphene-coated high-entropy oxide nanoparticle catalyst. This invention does not have special requirements for the carbon cloth; any carbon cloth well-known to those skilled in the art can be used. In a specific embodiment of this invention, the resistivity of the carbon cloth is 75 Ω; the preferred spreading amount of the metal salt and mesoporous carbon mixture on the carbon cloth surface is 10–500 mg / cm³. 2 More preferably 50–450 mg / cm³ 2This invention does not have special requirements for the size of the carbon cloth; it can be selected according to the mass of the mixture of metal salt and mesoporous carbon. In a specific embodiment of this invention, a 1cm × 5cm carbon cloth is used. In this invention, the Joule heating method preferably includes: connecting both ends of the carbon cloth to the positive and negative terminals of a power source, and performing Joule heating; the intensity of the current used is preferably 10–35A, more preferably 20–30A; the Joule heating is preferably carried out in an oxygen-containing atmosphere, preferably air or oxygen, more preferably air; the temperature of the carbon cloth surface after Joule heating is 1000–2000℃; the reaction time is ≤2s; after energizing, the carbon cloth surface rapidly heats up to the target temperature, causing the mixture of metal salt and mesoporous carbon spread on the carbon cloth surface to react, and the entire reaction process… The reaction is completed within 2 seconds. During the reaction, the metal salt is reduced to form a high-entropy alloy under the reduction of mesoporous carbon, and then oxidized by oxygen in the air to form high-entropy alloy oxide nanoparticles. At the same time, the mesoporous carbon is vaporized under high temperature conditions, and then a graphene layer is deposited on the surface of the high-entropy alloy oxide nanoparticles to form a graphene layer. Graphene has a porous structure. After encapsulating the high-entropy oxide, the electronic structure at the interface between the metal oxide and graphene will change, thereby affecting the catalytic activity. Furthermore, this invention uses Joule heating, which has an extremely fast heating rate and can avoid the formation of other alloy phases, thereby obtaining a single-phase high-entropy oxide.

[0030] After the reaction is complete, no further processing is required; simply collect the resulting product from the carbon cloth.

[0031] This invention also provides a graphene-coated high-entropy oxide nanoparticle catalyst prepared by the preparation method described above, comprising high-entropy oxide nanoparticles and a graphene layer coated on the surface of the high-entropy oxide nanoparticles; the metal element in the high-entropy oxide includes five elements selected from Fe, Co, Ni, Cr, V, Ti, Cu, and Mn, and the five metal elements are in an equimolar ratio, and the metal element in the high-entropy oxide is more preferably Fe, Co, Ni, Cr, and V (in this case, the high-entropy oxide is denoted as (FeCoNiCrV)O). x Alternatively, it could be Fe, Co, Ni, Cr, or Mn (in this case, the high-entropy oxide is denoted as (FeCoNiCrMn)O). x The size of the high-entropy oxide nanoparticles is preferably 5-10 nm.

[0032] This invention also provides the application of the graphene-coated high-entropy oxide nanoparticle catalyst described above in the catalytic electrolysis of water reaction; the electrolysis of water reaction is preferably an oxygen evolution reaction and a hydrogen evolution reaction or a total water electrolysis reaction; this invention does not have special requirements for the specific method of the application, and any method well known to those skilled in the art can be used.

[0033] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0034] Example 1

[0035] (1) Place 300 mg of mesoporous carbon and 15 mL of 68% concentrated nitric acid in a hydrothermal reactor and treat at 120 °C for 12 h. After cooling to room temperature, filter the mixture, then wash it three times by centrifugation with water, and dry it in an oven at 160 °C for 12 h to obtain clean mesoporous carbon.

[0036] (2) Weigh 80.8 mg Fe(NO3)3·9H2O, 58.2 mg Ni(NO3)2·6H2O, 58.2 mg Co(NO3)2·6H2O, 80 mg Cr(NO3)3·9H2O, and 24.4 mg NaVO3, and add 10 mL of deionized water to prepare a solution with a total metal ion concentration of 0.1 mol / L. -1 A mixed metal salt solution in which Fe, Co, Ni, Cr and V are present in equal molar amounts was prepared. 100 mg of clean mesoporous carbon was placed in 20 mL of the mixed metal salt solution, ultrasonically mixed for 4 h, and then dried in an oven at 60 °C for 8 h to obtain a mixture of metal salt and mesoporous carbon.

[0037] (3) Cut the carbon cloth into 1cm×5cm sheets, connect the positive and negative terminals of the power supply at both ends, and evenly spread the pentagonal metal precursor on the surface of the carbon cloth. Adjust the current of the power supply to 25A, and the carbon cloth will rapidly heat up to 1600℃. The metal salt and mesoporous carbon mixture spread on the surface of the carbon cloth will react to form a graphene-coated high-entropy oxide nanoparticle catalyst. The entire reaction process is completed within 2 seconds. The resulting catalyst is denoted as G@(FeCoNiCrV)O x .

[0038] Comparative Example 1

[0039] The traditional method for preparing catalysts is as follows:

[0040] The precursor was prepared using steps 1 and 2 in Example 1. The precursor was placed in a tube furnace and heated in an air atmosphere to 500°C and held for 60 minutes. After the heating was completed, it was naturally cooled to room temperature to obtain the carbon-supported metal oxide catalyst prepared by the conventional method.

[0041] Performance testing

[0042] (1) Morphological structure characterization

[0043] Transmission electron microscopy was used to examine G@(FeCoNiCrV)O prepared in Example 1. x The morphology of the catalyst was observed, and the results are as follows: Figure 1 As shown, according to Figure 1 It can be seen that the catalyst retains the graphene layer after high-temperature oxidation, the high-entropy oxide nanoparticles are dispersed on the surface of the graphene substrate, and the nanoparticles are wrapped by a multi-layer graphene structure, and the size of the high-entropy oxide nanoparticles is about 10nm.

[0044] (2) Phase analysis

[0045] XRD diffraction was used to analyze G@(FeCoNiCrV)O prepared in Example 1. x Phase analysis of the catalyst yielded the following results: Figure 2 As shown, the results indicate that G@(FeCoNiCrV)O x The catalyst is a single-phase oxide, a high-entropy oxide with sharp diffraction peaks, and also contains diffraction peaks of carbon.

[0046] (3) Oxygen evolution performance test

[0047] The G@(FeCoNiCrV)O prepared in Example 1 was used respectively. x The catalyst and the catalyst prepared in Comparative Example 1 were tested for the oxygen evolution reaction in water electrolysis. The specific operation method is as follows: a three-electrode system was used for testing, with Hg / HgO as the reference electrode, a carbon rod as the counter electrode, and the catalyst coated on a glassy carbon electrode as the working electrode. The linear scan curve was tested in 1M KOH solution, with a scan voltage range of 1.2 to 1.8 V vs. RHE.

[0048] Test results show that at 10mA cm -2 At current densities, G@(FeCoNiCrV)O was used. x The catalyst used in the oxygen evolution reaction of water electrolysis exhibited an overpotential of 246 mV, while the catalyst prepared using traditional methods showed an overpotential of 383 mV. The catalyst using G@(FeCoNiCrV)O x The catalyst catalyzes the oxygen evolution reaction in water electrolysis, and its oxygen evolution overpotential is 137 mV lower than that of catalysts prepared by conventional methods, indicating that the catalyst of the present invention has superior catalytic activity.

[0049] (4) Hydrogen evolution performance test

[0050] The G@(FeCoNiCrV)O prepared in Example 1 was used respectively. xThe catalyst prepared in Comparative Example 1 catalyzes the hydrogen evolution reaction of water electrolysis. The specific operation method is as follows: a three-electrode system is used for testing, and an electrochemical workstation is used for testing. Hg / HgO is used as the reference electrode, carbon rod is used as the counter electrode, and the catalyst is coated on a glassy carbon electrode as the working electrode. The linear scan curve is tested in 1M KOH solution, and the scanning voltage range is -0.1 to -0.5V vs. RHE.

[0051] Test results show that at 10mA cm -2 At current densities, G@(FeCoNiCrV)O was used. x The catalyst used in the hydrogen evolution reaction of water electrolysis produced an overpotential of 257 mV, while the catalyst prepared by the conventional method produced an overpotential of 485 mV for the oxygen evolution reaction of water electrolysis. The catalyst using G@(FeCoNiCrV)O x The catalyst for the hydrogen evolution reaction of water electrolysis exhibits a hydrogen evolution overpotential that is 228 mV lower than that of catalysts prepared by conventional methods, indicating that the catalyst of this invention has superior catalytic activity.

[0052] (5) Total hydrolysis reaction

[0053] GO@(FeCoNiCrV)O prepared in Example 1 x The catalyst catalyzes the total water splitting reaction, and the specific operation method is as follows: a two-electrode system is used for testing, and an electrochemical workstation is used for testing. The catalyst is coated on glassy carbon electrodes as the two electrodes of the electrolytic cell, and the electrolysis voltage is tested in 1M KOH solution.

[0054] The results showed that at 100mA cm -2 At a current density, G@(FeCoNiCrV)O prepared in Example 1 was used. x The catalyst catalyzes the total water splitting reaction, with an electrolysis voltage of 1.7–1.8 V, and exhibits excellent catalytic activity.

[0055] (6) Stability (or service life) test

[0056] The test method for the complete water splitting reaction was adopted, at a current density of 100 mA cm⁻¹. -2 Under the specified conditions, the electrolysis voltage under constant current was tested. After the catalyst had been working stably for more than 100 hours, the electrolysis voltage did not change significantly.

[0057] Example 2

[0058] The other conditions are the same as in Example 1, except that the current is changed to 15A and the surface temperature of the carbon cloth is 1200°C.

[0059] The catalyst prepared in Example 2 was tested for oxygen evolution reaction and hydrogen evolution reaction using the aforementioned method. The test results are as follows: Figure 3 As shown, Figure 3 (a) shows the oxygen evolution reaction test results, and (b) shows the hydrogen evolution reaction test results, at 10 mA cm⁻¹. -2 At the given current density, the overpotentials for the oxygen evolution reaction and the hydrogen evolution reaction are 280 mV and 348 mV, respectively.

[0060] Example 3

[0061] The other conditions were the same as in Example 1, except that the metal salt NaVO3 was replaced with Mn(NO3)2, and the amount was 0.2 mmol.

[0062] The catalyst prepared in Example 3 was tested for oxygen evolution reaction and hydrogen evolution reaction using the aforementioned method. The results showed that at 10 mA cm⁻¹, -2 At the given current density, the overpotentials for the oxygen evolution reaction and the hydrogen evolution reaction are 250 mV and 256 mV, respectively.

[0063] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a graphene-coated high-entropy oxide nanoparticle catalyst, characterized in that, Includes the following steps: Mesoporous carbon and a mixed metal salt solution are mixed and then dried to obtain a mixture of metal salt and mesoporous carbon; the metal elements in the mixed metal salt solution are Fe, Co, Ni, Cr and V, or Fe, Co, Ni, Cr and Mn, and the molar amounts of each metal element are equal. The mixture of the metal salt and mesoporous carbon is spread on the surface of carbon cloth, and the carbon cloth is Joule heated to cause the metal salt and mesoporous carbon to react, thus obtaining a graphene-coated high-entropy oxide nanoparticle catalyst.

2. The preparation method according to claim 1, characterized in that, The Joule heating method includes: connecting the two ends of the carbon cloth to the positive and negative terminals of a power source, and performing Joule heating by energizing the cloth; the intensity of the current used for energizing the cloth is 10~35A.

3. The preparation method according to claim 1 or 2, characterized in that, The Joule heating is carried out in an oxygen-containing atmosphere; the temperature of the carbon cloth surface after Joule heating is 1000~2000℃; the reaction time is ≤2s.

4. The preparation method according to claim 1 or 2, characterized in that, The mixture of metal salt and mesoporous carbon is spread at a rate of 10~500 mg / cm² on the carbon cloth surface. 2 .

5. The preparation method according to claim 1, characterized in that, The total concentration of metal ions in the mixed metal salt solution is 0.01~0.1 mol / L; the ratio of mesoporous carbon to mixed metal salt solution is 5~25 mg:1 mL.

6. The preparation method according to claim 1, characterized in that, The mesoporous carbon is pretreated before use; The pretreatment method includes: mixing mesoporous carbon and nitric acid for heat treatment, and then washing and drying the heat-treated mesoporous carbon in sequence.

7. The graphene-coated high-entropy oxide nanoparticle catalyst prepared by the preparation method according to any one of claims 1 to 6 comprises high-entropy oxide nanoparticles and a graphene layer coated on the surface of the high-entropy oxide nanoparticles; wherein the metal element in the high-entropy oxide is Fe, Co, Ni, Cr and V, or Fe, Co, Ni, Cr and Mn.

8. The application of the graphene-coated high-entropy oxide nanoparticle catalyst according to claim 7 in the catalytic electrolysis of water.

9. The application according to claim 8, characterized in that, The water electrolysis reaction is an oxygen evolution reaction, a hydrogen evolution reaction, or a complete water electrolysis reaction.

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